The present invention concerns a furnace or heating ladle for holding of liquid metals, in particular metals having a high melting point, such as cast irons, steels, or superalloys.
In particular, the invention relates to ladles of the type comprising a main element incorporating a cavity delimited by a heat-resistant lining and intended to be filled with molten metal, this cavity being fitted with a filling opening and a metal-outlet orifice connecting with said cavity, and metal-heating means. The cavity is intended to be filled with molten metal whose temperature is kept constant.
Conventional practice entails keeping liquid metal at constant temperature by using an electric tunnel furnace (see, for example, U.S. Pat. No. 3,810,564).
In this type of furnace, the holding the metal at constant temperature is effected by circulating the metal in a duct heated by an inductor. It is difficult to implement this technique when dealing with metals which require high holding temperatures, such as steels and superalloys. When in use, this type of furnace exhibits problems relating to the strength of the heat-resistant material composing the tunnel.
With some alloys such as treated cast irons, malfunctions occur, in particular those caused by substance build-up.
Furthermore, in tunnel furnaces, the quantities of refractory are significant, thereby mandating that a heel or the furnace be left continuously at constant temperature; accordingly, the use of the tunnel furnace is limited to a small number of applications not requiring a high degree of flexibility of use. For example, it is difficult to change alloys frequently or to shut down the furnace face every day.